Head-Worn Display Pose Prediction for Latency Compensation
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Solution Overview
Problem
Existing head-worn displays face challenges in accurately rendering earth-fixed symbology due to display system latency, particularly during sustained head motion, which can cause earth-fixed symbology to drift from conformal alignment.
Innovation Solution
A system and method for predicting head pose by projecting current head pose estimates forward in time based on angular rate/acceleration measurements and system display latency estimates, using a head-mounted IMU and body-mounted IMU, along with optical flow sensors, to reduce perceived latency and risk of hazardous misleading information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pose prediction is applied to counteract HWD system latency during sustained head motion, then conformal alignment of earth-fixed symbology is maintained, but system complexity increases due to projection algorithms and additional sensors
Solution Approach 1:
The system performs pose prediction by projecting current head pose estimates forward in time based on angular rate and acceleration measurements. This preliminary action compensates for display system latency before the latency error accumulates, maintaining conformal alignment without requiring real-time reactive corrections
Solution Approach 2:
The patent introduces an intermediary prediction algorithm that acts as a mediator between raw sensor measurements and final display rendering. This intermediary processing layer uses angular rate and acceleration data to estimate future head pose, bridging the gap between current sensor readings and future display requirements
2Measurement precision
If projection time is increased to maintain accuracy during high head motion, then conformal alignment is preserved, but perceived latency increases causing motion sickness and user discomfort
Solution Approach 1:
The system dynamically adjusts the projection time based on current head motion characteristics. During high sustained head motion, longer projection times are used to maintain accuracy, while during low motion periods, projection time is reduced to minimize perceived latency. This dynamic adaptation allows the system to optimize both accuracy and user comfort in different operational contexts
Solution Approach 2:
The patent changes the projection time parameter adaptively based on head motion levels. By monitoring angular rate and acceleration measurements, the system modifies the projection time parameter to balance between maintaining conformal alignment accuracy and minimizing perceived latency, thereby resolving the contradiction between these two requirements
3Measurement precision
If multiple IMUs and optical flow sensors are used to improve pose prediction accuracy, then measurement precision increases, but device complexity and cost increase
Solution Approach 1:
The patent combines data from multiple sensor types (head-mounted IMU, body-mounted IMU, and optical flow sensors) into a unified pose prediction framework. By merging these sensor inputs, the system achieves higher measurement precision through sensor fusion, where the complementary strengths of each sensor type compensate for individual weaknesses and reduce overall system complexity compared to using a single high-performance sensor
Data Source
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AI summary
A system and method for predicting an estimated head pose solution of a head worn display (104), HWD, at a future time selects or determines, for each HWD rotational axis, a relative angular rate of a head reference frame relative to a body reference frame. By sampling the relative angular rate, a relative angular acceleration is determined. Based on a projection time associated with estimated display latency, angular increment vectors for each rotational axis are determined for relative angular rate and relative angular acceleration. The current head pose solution is adjusted with respect to one or more axes based on the angular increment vectors to project the head pose estimate ahead based on the projection time, the resulting projected head pose solution corresponding to a predicted orientation of the head frame relative to the body frame at the future time.